A timeline of freedom of movement in the European Economic Area

The European Economic Area (EEA) provides a common market for goods, labour, services, and capital. Promoting integration between countries through the free movement of labour, or more generally persons, pre-dates the previous forms of the EEA. However, during the Southern and Eastern Expansions of the European Union, there have been transition agreements on persons, designed to restrict immigration. Opening up labour markets to the new member states with significantly lower GDP per capita than existing states, has been contentious. This is why the use of transition agreements have permitted periods which existing members can limit immigration. Not all existing member states impose restrictions, and during the Eastern Enlargements, the restrictions were imposed for varying lengths of time by different existing members up to a maximum of seven years. During the transition agreement, the economies of new members and existing members can converge, which is ultimately designed to limit the pull factor of migration. In this note, we provide a concise resource of the timeline of the expansion of full free movement of persons for countries in the EEA and Switzerland.


Introduction
The European Single Market includes the 27 countries of the European Union (EU) and the European Free Trade Association (EFTA) countries of Iceland, Liechtenstein, Norway, plus Switzerland. 1 Until 2020, the EU included the UK.The Single Market promotes the free movement for goods, labour (alternatively persons), services, and capital.However, joining the Single Market has not always been as simple as joining and gaining immediate access to all forms of free movement, especially labour, as existing member states (EMS) have.This prime example of international co-operation and international integration can come with caveats.Transition agreements on free movement of labour have been implemented on the countries joining the EU in 1981, 1986, 2004(except Cyprus and Malta), 2007, and 2013.The transition agreements are in place to stop large shocks to the labour markets and population of EMS.The transition periods can last up to seven years, in which time it is probable that the economies of new member states (NMS) have improved to be closer to EMS.The restrictions on free movement of labour were in conventional sense only, which enabled exceptions and ways to work around the restrictions.As a result of restrictions, there should be reduced incentive to migrate.The 15 members that joined the EU before 2004 are commonly referred to as the EU15.The expansion, exit of the UK, candidate and potential candidate countries of the EU is shown in Table 1.
This paper provides a concise resource as to which years single market entry and freedom of movement was first obtained to enable researchers to easily access the information.Section 2 describes the methodology employed; Section 3 presents the expansion of the common market, and other relevant unions; and contains the years freedom of movement was gained; and Section 4 discusses possible future expansions and challenges.

Study design
The most suitable approach for this research is a document analysis of the 32 countries of the EU+ in 2019.Further, in the Eastern Expansions since 2004, there has been differing results across the EMS.The primary method used is document analysis -the exact sources are detailed in the next sections.To formulate a timeline of freedom of movement, we proceed with two main questions: (i) what date did a country join the common market and (ii) was that country granted immediate freedom of movement for persons.If the answer for the second question is negative, we are required to explore further sources to find the years which full access was granted.Early research stages required creating a timeline of the evolution of the EEA (as detailed in Section 3).It is important to note that the restrictions on free movement of labour were on workers specifically and not all types of migration.As services are not subject to restrictions, it is possible for self-employed workers to move or establish themselves while their home country is under transition restrictions.A founding legal case from 1990 brought by a Portuguese company to the European courts determined that the Portuguese company was entitled to bring its own workers to France to complete the works that the firm had been contracted to do, instead of hiring French workers (European Court, 1991;Marshall, 1991).This was at a time when Portugal was under a transition agreement.The ability for self-employed Polish workers, even doctors, to work in Germany is discussed in Fellmer (2008); the process was replicated across countries that imposed restrictions.

Source selection
To gather information for the timeline on the expansion of the European Common Labour Market, we begin by researching the timeline of what is currently known as the EEA.The EU provides a record of legal agreements on EUR-Lex which the majority of treaties included in this research are available.For information not available from EUR-Lex, we source from other government sources, academic literature or reports from official organisations.

Data collection
The analysis of the downloaded documents took place in July and August 2021.The conclusion of the research occurred when Table 2 and Table 3 were complete.The full list of sources by country is available in the data accompanying this research (Barker, 2022).The treaties covered most of the details, however, some were details that could be subject to change. 2 The treaties were chosen as they are the legal documents and available from credible sources.

Analysis
The data analysis method employed is basic quantitative content analysis, in which we search the required documents for the dates to answer the questions outlined in our study design.The dates gathered from this research are used to create Table 2 and Table 3.In addition, the exact dates (not only years) Barker and Bijak (2021) used to create a variable for the effective labour market size for EEA states and Switzerland for the purpose of the investigation of the effects of net immigration or net emigration on the macroeconomy.As there has been considerable expansion of the EEA since the start of the sampling period (2002), this needed to be reflected as an exogenous variable in that model.It was important to identify the dates that countries joined the bloc (and exited in the case of the UK) to reflect the joining of new members and their labour force size.For example, when the A8 countries joined in 2004, there was a significant increase in migration to Ireland, Sweden and the UK because those countries did not place any limitations on movements.The other member states did impose limits, but for varying lengths of time which meant reflecting the changes was important.While it was necessary to the research to find the changes from 2002, to complete the research we backdated the start of the study to have an understanding of the origins and development of the European Common Market as of today.

Expansion of the common market
For each country we detail the year that they gained access to another country's labour market.In finding these years, we have several policies to extract analysis from which we gather the joining dates between two (or more) countries.
Below we list the main treaties and evolution of the common (labour) market.The agreements are signed and agreed by all the EMS and NMS up to years in advance of the NMS or changes occurring, by which time these are enshrined in national law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otes: Years that free movement of persons was first granted.The column shows the host country, with the row identifying the citizens of sending country.

European Coal and Steel Community (ECSC)
The UK ceased to be a member of the common labour market in 2020, though the original years are detailed here.Only Ireland and the UK have free movement.AUT 200419942004199420071994200720042006199419941994199519942007BEL 200419602004196020071992200720042006199219941994199519942007BGR 200720142014201420072009200720072007200920072012201220122016HRV 201320152018201820132013201320132018201520132015201820142022CYP 200420042004200420042004200720042004200420042004200420042007CZE 200420072004200720042006200720042004200620042009200920092011DNK 200419732004197320071992200720042006199219451955199519542007EST 200420072004200720042006200720042004200620042009200920092011FIN 200419942004199420061994200720042006199419491955199519542007FRA 200419682004196820071992200720042006199219941994199519942007DEU 200419682004196820071992200720042006199219941994199519942007GRC 200419882004198820061992200720042006199219941994199519942007HUN 200420072004200720042006200720042004200620042009200920092011IRL 200419732004197320041992200720042004199219941994199519942007ITA 200419682004196820061992200720042006199219941994199519942007LVA 200420072004200720042006200720042004200620042009200920092011LTU 20072004200720042006200720042004200620042009200920092011LUX 20042004196020071993200720042006199319941994199519942007MLT 20042004200420042004200720042004200420042004200420042007NLD 20041960200420071992200720042006199219941994199519942007POL 20042007200420072006200720042004200620042009200920092011PRT 20041993200419922006200720042006199219941994199519942007ROU 20072014201420142007200920072007200920072012201220122016SVK 20042007200420072004200620072004200620042009200920092011SVN 20042007200420072004200620072004200620042009200920092011ESP 20041993200419922006199220072004200619941994199519942007SWE 20041994200419942004199420072004200419941955199519542007ISL 20041994200419942007199420072004200619941945199519542007LIE 20041995200419952007199520072004200619951995199519952007NOR 20041994200419942007199420072004200619941945195519952007CHE 20062004200620042006200420092006200620042004200420042004UK 200419732004197320041992200720042004199219941994199519942007 Notes: Years that free movement of persons was first granted and for Switzerland the year that free movement with quotas was granted.The column shows the host country, with the row identifying the citizens of sending country.The UK ceased to be a member of the common labour market in 2020, though the original years are detailed here.Only Ireland and the UK have free movement.
following during (or after) the transition period for Spain and Portugal, due to the improved economic (and political) conditions (Royo, 2007), as such the transition period was reduced to six years (Council of the European Union, 1991 Liechtenstein The small country, or micro-state, in the centre of Europe is a unique case.A member of the EFTA in its own right, and a population of less than 40,000. 5Working in the country is unrestricted for EEA and Swiss citizens but gaining a residence permit is more difficult due to the limitations allowed (Cassis, 2012).Countries of a similar size, e.g., Andorra, Monaco, San Marino, and the Vatican City have agreements with the EU to be de facto members6 as well as using the Euro currency, while Liechtenstein uses the Swiss Franc.
The Withdrawal Agreement In 2016, the UK voted to leave the EU.The terms of agreement were finalised in 2020.In the results, we have included the years which access were granted by the UK to its labour markets and given to citizens of the UK in other European countries.Only citizens of the Republic of Ireland have free movement to the labour market of the UK and reciprocally to satisfy the Good Friday Agreement.
As a summary, Figure 1 shows the different economic groupings within Europe.The most recent county to join the Euro Area is Croatia, which changed over in 2023.The next members to join are likely to be Bulgaria and Czechia7 .
Table 2 and Table 3 show the year in which a country gained full access to the labour market of another country.The column heading is the country that the row applies to.The row shows what year citizens of that country gained access to the labour market of the country in the column heading.For example, cell B4 of Table 2 shows that Bulgarian citizens gained full access to the labour market in 2014, whereas in D2 Austrian citizens were able to access the Bulgarian labour market in 2007 as no reciprocal measures were in place.These are the original years that there was access, however, there are some changes where freedom was temporarily revoked as detailed in the section covering Switzerland and below.

Notes
Spain allowed access to Bulgarian and Romanian citizens in 2009, but Spain reintroduced restrictions for Romanian citizens on 22 July 2011, which were removed in 2014.
Switzerland has a safeguard clause in their agreements, such that they are able to suspend free movement or introduce quotas on permits.The original years for the UK remain as it is important to the history of the EU.The freedom of movement to and from the UK ends in 2020, except for Ireland.

Discussion
We have looked the evolution of the Single Market with a focus on the free movement of persons.This case study provides a resource for researchers looking at the history of the European common (labour) market, and future paths with respect to potential restrictions for future expansions.In light of the results presented in Table 2 and Table 3, it is clear that simply assuming that freedom of movement of workers and persons in the conventional sense was granted in the years of accession is incorrect.Only in the case of the founding members of the EEC and the 1972 and 1994 accession countries was this correct.For researchers studying migration in Europe, and to the wider European labour market, this gives a timeline of major changes.This is not to say that all future expansions will include restrictions, though as the next subsections will consider, this explains some foundations and likelihoods of expansion restrictions.When future expansions of the EU happen, researchers will be able to use this concise resource to see how previous expansions dealt with the restrictions on freedom of movement.In this section, we look at assessing the effectiveness of expansions, the potential future expansions and the challenges of integration.
Assessing the effectiveness Future potential members of the EU must consider whether joining the EU is of net benefit to the country, while the EU14 8 must evaluate the future of the EU in terms of potential reforms (Costa et al., 2023).Nevertheless, has joining the common market been beneficial?Macroeconomic based studies have shown that membership for the Central and Eastern European countries has beneficial as these countries have experienced economic convergence relative to the EU15 and accelerated economic growth since joining the common market driven by increased trade, foreign investment and government integrity (Nagy & Šiljak, 2022; Rapacki & Prochniak, 2019).The effects of labour are not studied to the same degree.To empirically analyse the effectiveness of the freedom of movement for labour on individual member states would be possible with extensive review of labour market data.This would highlight whether problems in the labour market, including (industry specific) labour shortages, have benefited from common market membership.There are two distinct groups within the common labour market: the net senders of migrants and net receivers of migrants.Migration is a contentious topic, particularly in the countries that have high net migration rates which has led to the aversion of further expansions as mentioned previously.The question that these countries must ask can be likened to Switzerland's position when negotiating the bilateral agreements: does the (perceived) trade-off for access to the common market for goods, services and capital exceed that for high levels of immigration?A conclusion from Switzerland can be seen that the trade-off is worth it.Though, if we consider the case of the UK, the Government pursued a complete exit from the common market.Opinion polls have seen a trend of increase to the opinion that the UK was wrong to leave the EU.It is important to note that Switzerland regularly has referendums, while the UK only had 8 The EU15 minus the UK.
one vote in 2016 and none to accept or reject the agreed deal.Both examples suggest that the trade-off is perceived to be worthwhile since recent polling has been done since the effects of the deal have become reality.From the opposing side, the candidate countries are all likely to face emigration if they were to join, as discussed above.Nevertheless, their governments see access to the single market beneficial even if there is large emigration.
Future expansions of the EU The candidate countries and potential candidate countries listed in Table 1 have varying degrees of likelihood.Some of the countries have a significant length to go to so that their politics aligns with EU directives, and in some cases the country to be fully recognised as an independent state by all current member countries.Noteworthy examples include Cyprus, Greece, Romania, Slovakia, and Spain not recognising Kosovo; and the issues of Turkey and Cyprus over the Turkish Republic of Northern Cyprus, and absence of Turkish-Cypriot diplomatic relations though negotiations with Turkey have been frozen9 Expansion of the EU is unlikely in the shortterm due to the status of negotiations with each candidate country only in early stages of negotiations10 , alongside opposition of founder EU members to further expansion as evidenced when a group of countries led by France blocked the opening talks with Albania and North Macedonia to the accession process in October 2019 citing the need for review and reform of the EU before any expansions can take place.11 For any future (Eastern) expansions, transitional agreements on persons would likely be imposed.These agreements, designed to allow the closing of the gap of NMS to EMS, are likely to be minimal due to the existing GDP per capita gap that exists.The real GDP per capita of Montenegro, North Macedonia, Serbia, Bosnia and Herzegovina, and Kosovo for 2019 was less than 25% of that of the EU-15, with Turkey at 37%. 12 The small closing of this gap will leave a pull factor to EMS, in particular the EU-14 and EFTA states, and possibly Slovenia.The inclusion of Slovenia towards EU-14 and EFTA states is due to their relatively high GDP per capita than other Eastern European countries, where wages and salaries are close to the levels of Greece, Italy, Portugal and Spain.
In addition, the fallout from Brexit within the UK raised questions over Northern Ireland and Scotland's membership ambitions.For Northern Ireland, there have been troubles associated with the Brexit agreement and Northern Ireland's requirements to satisfy the Good Friday agreement with the Republic of Ireland.In theory, there could be a reunified Ireland as one member of the EU.The Scottish National Party (SNP) asked for a second referendum to be held as recently as 2022, however, this was ultimately rejected by the UK Government, and soon after the UK Supreme Court ruled that a referendum cannot be held without UK Government approval. 13Scotland voted to remain in the EU in the Brexit referendum, but Scotland would be an entirely separate state with no immediate right to be in the EU/EEA. 14

Challenges of integration
With the recent rise in candidate countries, and belief that expansion of the EU is inevitable, it is important to consider problems that countries face during transitional stages from candidate country to full members.Countries joining the EU must align their social, economic and political status and beliefs with that of the EU, in particular democracy, human rights, and international cooperation.Further economic convergence is considered when a NMS joins the Euro currency.However, as shown in Figure 1, there are seven countries who have not adopted the Euro.Denmark negotiated an opt out and Sweden has no plans to, whilst the remaining five will join when they have met the necessary conditions. 15Czechia, Hungary and Poland have been EU members for 20 years but still have failed to meet the requirements to join the currency which shows how challenging it can be to align economic status.Georgia, Moldova and Ukraine applied to join the EU in the wake of Russia's invasion of Ukraine.Before Georgia became a candidate country, they had to address key clarifications whereas Moldova and Ukraine were granted candidate status immediately.From the perspective of a migrant, international migration is more challenging than domestic migration.The introduction of a common labour market has benefited millions of people, however, there are some issues that migrants encounter.One such struggle is a language barrier (Zalewski, 2021) -there are 24 official languages of the EU with more languages in use in the common labour market such as Icelandic, Norwegian, and regional ones.Having a poor command of the host country's language can be a barrier to employment or fully integrating into the community.Where a country has a positive attitude towards migrants, they are more likely to integrate (Naveed & Wang, 2021), however, with the rise of populism in Western Europe in particular, negative attitudes are likely to increase.
14 Previous separation proposals by the Scottish National Party made when the UK was a member of the EU argued that Scotland would be able to continue EU membership, that is no longer the case. 2 Faculty of Political Sciences, University of Zagreb, Zagreb, City of Zagreb, Croatia The article "A timeline of freedom of movement in the European Economic Area" written by Emily Barker represents a valuable resource for all scholars interested in the topic of freedom of movement, and particularly labor mobility within the EU/EEA.The empirical contributions in Table 2 and Table 3 can serve as a starting point for qualitative and quantitative research into a variety of topics, including determinants of variation in the duration of labor market access restriction by countries (or country groups), conditions for using reciprocal measures etc. Whilst this version of the manuscript is mostly well-written and sound, I am of the opinion that there are still some minor issues which need to be addressed before this paper becomes the final version.These smaller interventions would improve the manuscript even further.
-First, a note on this sentence from the intro: ''However, joining the Single Market has not always been as simple as joining and assuming equivalent status as Existing Member States (EMS)''.From this sentence, it is not entirely clear whether the author considers all four freedoms in the single market to be equally difficult to access for new Member States (NMS) or does this only apply to free movement of labor.Please clarify accordingly.
-in the first sentence of the methodology, the paper claims to conduct a multiple case study.I strongly advise against this claim because it does not reflect the reality and doesn't do justice to what case study methodology and research look like.Multiple case studies are in-depth, qualitative investigations.I believe you can leave this claim out and refer to document analysis of all countries observed in this paper as a data collection method, and quantitative content analysis as the method of data analysis.
-related to the previous point, it also seems to me from the description of the methodology and the presented results that the author actually conducted 'quantitative content analysis' instead of 'qualitative content analysis' as argued in the Analysis section.I suggest the author further looks into the differences between the two methodological approaches, and cites the relevant literature.
Given the fact that this article observed documents and coded explicit dates in various documents (accession treaties, safeguard agreements etc.), this approach differs from qualitative content analysis in which latent meanings are extracted from the text to generate categories.
-the paragraph which discusses the Treaty of Accession leaves out (without an explanation why) a discussion of the 2007 and 2013 enlargement cycles.In the same paragraph, the author forgets to mention that Croatia also applied reciprocal restrictions, which is also evident from Table 2 and Table 3.
-Given how controversial the topic labor mobility has been in Swiss-EU relations, a broadening of that specific paragraph on p 7/11 is warranted.An explicit reference to the Agreement on the Free Movement of Persons from 2002 is needed.This agreement foresees a gradual opening of the Swiss labor market and a quota system.In the case of Croatia, the European Commission and Croatia repeatedly asked for restrictions to Croatian citizens to be lifted after Croatia's entry into the EU in 2013, however a ban applied until 2021, only to be reapplied/reintroduced in 2023.
-please clarify in the note or in the title of Table 2 and Table 3 whether they show the years in which the treaties/agreements foresaw a lifting of restriction, that is, the granting of free movement or do they reflect the actual years when the free movement was granted.Look at the case of Croatia -the table writes that Croatian citizens could access the Swiss labor market only from 2024 -which is inaccurate.Please see previous point for reference.Formally, the Swiss safeguard clause for Croatian nationals can be applied until 2024, however free movement was granted already in 2022.The fact that new quotas were reintroduces for Croatians starting 2023 does not deny the fact that restrictions were lifted at the end of 2021.Please clarify and if needed, include separate figures in brackets for cases where there is a discrepancy in the theoretical and actual revocation of mobility restrictions on the labor market.
-Figure 1 should be updated to reflect the fact that Croatia entered the Eurozone starting 1 January 2023.Equally, the number of EA countries should be updated to 20.Related to this point, please also correct the numbers in the final section on ''Challenges of integration'' -seven countries have not adopted the euro, and five are still to join (excluding Denmark and Sweden).

Dion Kramer
Vrije Universiteit Amsterdam, Amsterdam, North Holland, The Netherlands By providing a clear overview of the opening of labour markets to new (EEC/EU/EEA/EFTA) Member States, this article offers a useful addition to the literature on the history of free movement and will be a useful resource for scholarship on free movement and migration.I have three main points for improvement.
-My main point is a lack of engagement with the (mostly legal) literature pointing at such phenomena as posted work and self-employed work.While workers are typically restricted from entering the labour markets of other Member States during transition agreements, there are typically no restrictions on the free movement of services and establishment.The famous Rush Portuguesa judgment is an example of this: while Portugal was still subjected to transition arrangements, Portuguese companies could already provide services and bring their Portuguese workers to other Member States for that purpose.Same goes for establishment: e.g., Polish citizens could set up a company and start economic activities as self-employed workers in other Member States.In other words: restrictions were merely imposed on the the free movement of workers and not all forms of migration itself (as suggested in the paper).For a comprehensive understanding of (the effects of) transition agreements, the difference between these forms of labour mobility seem pertinent to address.
-The discussion/conclusion does not seem to follow necessarily from the findings/results of this paper.One could arguably reflect on the prospect of free movement after (future) accession(s), but could one really reflect on the prospect of accession itself based on the findings?I am not saying that the discussion in its present form is not interesting, but how do your findings specifically add to the wider debate around accession?For one, the Russian war against Ukraine has accelerated the potential and the process of accession, of both Ukraine and other CC and PCCs.Additionally, I struggle to see the relevance of the final subsection on integration in light of the contribution of the article.This brings us to the main point: what is the added value of such a timeline?Perhaps this could be explicated better.
-Stylistic: There are some typo's and informal use of language ("aren't").Additionally, I would personally refrain from using abbreviations, especially since there are so many.The article is relatively short and the reader will not benefit from reading abbreviations like CC, PCC, ToA, NMS, EMS, etc.

Is the work clearly and accurately presented and does it engage with the current literature? Partly
Is the study design appropriate and is the work technically sound?Yes

Are sufficient details of methods and analysis provided to allow replication by others? Yes
Are all the source data and materials underlying the results available?Yes If applicable, is the statistical analysis and its interpretation appropriate?Not applicable

Are the conclusions drawn adequately supported by the results? Partly
Competing Interests: No competing interests were disclosed.

Francesco Paolo Mongelli
Goethe University, Frankfurt, Germany In my view, the article "A timeline of freedom of movement in the European Economic Area" by Emily Barker provides a very useful support in the discussion and analysis of an indispensable plank of the Single Market: the freedom of mobility within the European Union but also across EFTA and the wider European Economic Area.On one hand, this might support further research into the actual transposition of EU/EEA legislation into national law and the adoption of national decrees to support freedom of movement.On the other hand, it might support research into actual labour mobility across EU/EEA member states.My prior is that freedom of movement might be higher among EU member states, but should still be significant among EEA states: this is an empirical question.
Major points: Would be helpful to clearly distinguish between ratifications, adoption into national law, transposition with help of implementation decrees, enabling provision(s), and so on.Reviewer Expertise: Economic integration and monetary policy I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

○
Concerning Table2, I am perplexed by the NA: keep blanks instead?Figure1is about the EMS (nice figure by the way).○In the end implementation of the SM is a matter of degrees and modulation: what might subsequent empirical analysis show in terms of effective labor mobility?○In the discussion: vague language when mentioning "...align their social, economic and political factors."Which factors?○Minor points:The Single Market aims at/promotes....○It should be "member states".○Iam not sure that Liechtenstein would appreciate being labelled as an "anomaly", may be unique case?○Please take out or redraft Footnote 7: not sure UK might appreciate.○Is the work clearly and accurately presented and does it engage with the current literature?YesIs the study design appropriate and is the work technically sound?YesAre sufficient details of methods and analysis provided to allow replication by others?PartlyAre all the source data and materials underlying the results available?YesIf applicable, is the statistical analysis and its interpretation appropriate?PartlyAre the conclusions drawn adequately supported by the results?YesCompeting Interests: No competing interests were disclosed.

Table 1 . Expansion of the European Union. Expansion of the EU Brexit CC PCC 1958 1973 1981 1986 1995 2004 2007 2013 2020
CC: candidate countries; PCC: potential candidate countries.The development of the European Union and the possible future members.In June 2022, Moldova and Ukraine were granted Candidate Country status, Bosnia and Herzegovina in December 2022, and Georgia in December 2023.Correct as of March 2024.Source: European Union and European Commission

European Economic Community (EEC) The EEC
The founder members were Belgium, France, Italy, Luxembourg, the Netherlands, and West Germany.The Treaty establishing the European Coal and Steel Community Treaty came into force on 23rd July 1952 (Publications Office of the European Union,1951).This covered workers from only certain industries, thus not enabling full freedom of movement.

Table 3 . Expansion of Freedom of Movement (2). Sending Country Receiving Country LTU LUX MLT NLD POL PRT ROU SVK SVN
).The countries in the 2003 Treaty included Cyprus, Czech Republic, Estonia, Latvia, Lithuania, Malta, Poland, Slovakia, and Slovenia.Citizens of Cyprus and Malta were allowed immediate access to all the EU15 and EFTA (except Switzerland) labour markets, but the remaining eight countries were not guaranteed this.Only Ireland, Sweden, and the UK fully opened their markets.Nations could impose restrictions on workers being able to access the welfare state.The 2005 Treaty included Bulgaria and Romania, for both countries there were restrictions on freedom of movement from most of the same countries as before, plus Hungary Ireland, Malta and the UK.The 2011 Treaty covered Croatia's accession which again featured restrictions on full freedom of movement.The transition agreements permitted the NMS to employ reciprocal restrictions, which only Hungary, Poland and Slovenia of the A8 countries did (Goldner Lang, 2008) and latterly Croatia.Croatia was stricter about the reciprocal restrictions as the three A8 countries lifted them all by 2009 at the latest, even though Austria and Germany stilled imposed the restrictions until 2011.Malta were under the quota scheme for 2006-2007.Free movement with safeguard clauses lasted until 2013, when the safeguard clause was activated for a year, and since deactivation, there has been full freedom of movement.The Eastern Expansions are subject to further delays on accessing the Swiss labour market.The A8 countries experienced national worker priority from 2006 to 2011, when free movement with clauses was attained for one year, until the invocation of the clause from 2012-2014.Since 2014, there has been free movement of persons without limitations.Bulgaria and Romania were subject to national worker priority from 2009 to 2016, one year of safeguard clauses before two years where the invocation of a safeguard clause.This was lifted in 2019, with full freedom of movement since.Croatia experienced country specific quotas from 2014 to the end of 2016, from 2017 to the end of 2021, there was national worker priority.Switzerland applied the permit system for Croatia, starting in 2022, on a trial basis.In 2022 and 2023, the immigration of Croatian nationals was at a level that the safeguard clause was activated to impose quotas for 2023 and 2024 4 .The plan is to lift the quota for 2025 and 2026 before allowing freedoms without limitations in 2027.To be consistent across countries, and the definition in European Communities (1999), we use the free movement with safeguard clauses in our research.
European Economic Area (EEA) EEA includes the EU countries, Iceland, Liechtenstein, and Norway the agreement came into force on 1st January 1994.Austria, Finland and Sweden joined the EEA before subsequently joining the EU in 1995.The agreement brought the countries into the Single Market for the four freedoms.Not all of the EU policies were included in the agreement.EFTA today consists of Iceland, Liechtenstein, Norway, and Switzerland.

Traité instituant l'Union économique Benelux (Treaty of the Benelux Economic Union
Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).research project that is funded by the European Union's Horizon 2020 research and innovation programme under grant agreement No. 870299.All the remaining errors and inaccuracies are the author's.This document reflects the author's view and the Research Executive Agency of the European Commission are not responsible for any use that may be made of the information it contains.
15 Source: European Union, Accessed 16 September 2021 ).Treaty, 1958; First accessed 19 July 2021.Reference Source Cassis I: Report: Free Movement of Workers.Report 1116899, European Free Trade Association, 2012.Reference Source Condinanzi M, Lang A, Nascimbene B: Citizenship of the Union and Freedom of Movement of Persons.Martinus Nijhoff Publishers, Leiden, The Netherlands, 2008.Reference Source Costa O, Schwarzer D, Beres P, et al.: Sailing on High Seas: Reforming and Enlarging the EU for the 21st Century.Technical report, Franco-German Working Group on EU Institutional Reform, 2023.

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presented and does it engage with the current literature? Yes Is the study design appropriate and is the work technically sound? Yes Are sufficient details of methods and analysis provided to allow replication by others? Yes Are all the source data and materials underlying the results available? Yes If applicable, is the statistical analysis and its interpretation appropriate? Not applicable Are the conclusions drawn adequately supported by the results? Yes Competing Interests:
No competing interests were disclosed.